NO-SOLICITING Notification of no soliciting MAY [No-soliciting]
And a new reference in Section 13:
[No-soliciting] C. Malamud, "A No Soliciting Simple Mail Transfer
Protocol (SMTP) Service Extension", RFC 3865,
September 2004.

Issues with References:
a) Section 12 of RFC 4409 contains the entry:
[ESMTP] Klensin, J., Freed, N., Rose, M., Stefferud, E.,
and D. Crocker, "SMTP Service Extensions", STD 10,
RFC 1869, November 1995.
`STD 10` in fact should be `(ex) STD 10` according to rfcxx00.txt .
The material from RFC 1869 has been incorporated into RFC 2821,
and RFC 1869 has been reclassified to Historic.
Therefore, this reference should not have been listed as a
Normative Reference. The Ref. to RFC 2821 in fact catches all.
Section 12 of RFC 4409, under [SMTP-MTA] also contains the entry:
Partridge, C., "Mail routing and the domain
system", STD 10, RFC 974, January 1986.
`STD 10` in fact should better have been `(ex) STD 14` --
rfcxx00.txt says: "Now Historic." ^^
The non-obsolete material from RFC 974 has been incorporated
into RFC 2821 and RFC 974 has been reclassified as Historic.
Therefore, this reference should not have been listed as a
Normative Reference. The Ref. to RFC 2821 in fact catches all.
Finally, the subsequent entry,
Braden, R., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, October
1989.
also is not needed any more, because the SMTP related material
in RFC 1123 has been revised and incorporated into RFC 2821
as well. The Ref. to RFC 2821 in fact catches all.
b) Section 13 of RFC 4409, under [MESSAGE-FORMAT] contains the entry:
Braden, R., "Requirements for Internet Hosts -
Application and Support", STD 3, RFC 1123, October
1989.
Similarly to the last item above, the IMF related material from
RFC 1233 has been revised and incorporated into RFC 2822; thus
this Ref. is not really needed any more.
The Ref. to RFC 2822 in fact catches all.
c) Section 13 of RFC 4409 contains the entry:
[IPSEC] Kent, S. and R. Atkinson, "Security Architecture
for the Internet Protocol", RFC 2401, November
1998.
This Ref. was already outdated at the time of publication of
RFC 4409; it should point to the current IPSEC Architecture
document, RFC 4301 !
BTW:
This apparently is a `viral` legacy issue -- RFC 2476 also
contained an outdated Ref., to the predecessor of RFC 2401 !